Sit-Stand Chair

ABSTRACT

The present invention is a sitting device that gives the user an option to sit with one side of his/her lower portion of the body (e.g., buttock, thigh and leg) supported by a half seat, while maintaining a standing posture with the unsupported leg. Since the standing posture naturally keeps the lumbar lordosis, the device eliminates the source of sitting-related back pain. In an embodiment, the sitting device includes two half seats that can be raised or collapsed individually, and a foot stool for the foot to rest in case it is raised. The user can change the positions of the half seats manually by pushing one of the provided buttons. Or it can be automatic if the user uses a controller to program how frequently the half seats alternate, or both of them be in supporting position at the same time to use the device as an ordinary chair.

FIELD OF THE INVENTION

The present invention relates to chairs, chair-like devices, body support devices, standing devices, and sitting devices. More specifically, the present invention is a sitting device.

BACKGROUND OF THE INVENTION

According to a study (Deyo et al., 2006), about one fourth of U.S. adults report low back pain in the past 3 months, emphasizing the prevalence and importance of this condition. It is generally accepted that prolonged, static sitting postures are likely to aggravate a preexisting low back condition or instigate the development of a new condition (Kelsey & White, 1980; Lis et al., 2007; Battié et al., 2002). Also, a recent occupational study finds that sitting hours positively correlate with lower back pain (Mendelek et al., 2011). In sitting, the pelvis rotates posteriorly and the lumbar lordosis flattens (De Carvalho et al., 2010). This posture increases the strain on the posterior passive elements of the spine (De Carvalho et al., 2010; O'Sullivan et al., 2011; Lengsfeld et al., 2000). The problem stems from the very fact that chair sitting requires raising both upper legs. This reduces the angle between the thigh and the torso from 180 degrees to near 90 degrees therefore pushing the posterior passive elements of the spine (De Carvalho et al., 2010).

There are some claver chair products increasing the thigh-torso angle by providing a knee support and a forward-tilted seat (U.S. Pat. Nos. 4,765,684; 5,782,534), thereby reducing back pain. Another category of products is standing chair (U.S. Pat. Nos. 3,704,847; 4,738,487), by which the user maintains a half-standing posture; sitting on a raised, tilted-forward seat. There are other inventions which let the user change the thigh-torso angle by having two split half seats individually tilt forward (U.S. Pat. Nos. 4,451,086; 7,387,339 B2) or mobilizing the pelvis (U.S. Pat. Nos. 6,139,095; 6,357,827 B1) while the user is in a sitting position. While these products increase the spine-thigh angle, they do not reach the ideal 180 degrees (standing posture); and the postures that the user needs to maintain are rather unnatural.

SUMMARY OF THE INVENTION

The applicant has invented a new category of chair or sitting device, which provides, in one embodiment, two half seats that are individually controlled to be in a supporting seat position or in a collapsed seat position. The sitting device effectively lets the user keep the standing posture while at least half of the body weight supported. Since the standing posture naturally keeps the lumbar lordosis, the sitting device eliminates the source of sitting-related back pain. Moreover, it also gives the user an option to use it as an ordinary chair by positioning both of the two half seats in the supporting position.

In a first embodiment, the sitting device includes two independently position-adjustable half seats. The half seats are secured to the seat support frame comprised of a horizontal cross bar and a vertical guide tube. The piston of a pneumatic cylinder or any equivalent mechanism, which is for height adjustment of the whole sitting device, is housed and travels inside the vertical guide tube of the seat support frame. The bottom of the pneumatic cylinder is secured to the base of the sitting device. At the lower portion of the vertical guide tube of the seat support frame, two perches are attached one for the left half seat-controlling actuator and the other for the right half seat-controlling actuator to be secured on. The bottom of the half seat-controlling linear actuator is secured to the perch via a bracket; the top part of the actuator is secured to the bottom of the half seat via a bracket. The position of each half seat is controlled by the length of the linear actuator, which in turn is controlled by the user via manual switches or by a programmable control box.

A second embodiment of the sitting device shares most of the mechanisms of the first embodiment except for the half seat moving mechanism. In the second embodiment, the linear actuators of the first embodiment are replaced with rotors with attached seat supporting arms, which control the positions of the half seats. Each seat supporting arm has two segments (lower part and upper part) with a joint in the middle. The bottom of the arm is attached to the rotor; the top end of the arm is attached to the bottom of the half seat via a bracket. The position of each half seat is controlled by the angular position of the rotor which in turn swings the attached supporting arm. When the supporting arm swings forward, the attached half seat rises to a supporting position; when the supporting arm swings backward, the attached half seat retracts. This swinging motion is controlled by the user via manual switches or by a programmable control box. Other alternate designs are also presented.

The sitting device of any embodiment may further include one or more of the following: a height fixing mechanism, a backrest or back support member, armrests or arm support member, any structural reinforcement mechanism, casters, a foot stool or foot support member, and any safety mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a one side view of the first embodiment of the invention, illustrating one half seat in a supporting position on which a user sits while he/she stands with the other leg. In the following figures, the foot stool has been removed for clarity.

FIG. 2 is an exploded, perspective view of a height adjustment mechanism of a sitting device according to the present invention, illustrating the seat support frame (upper portion), and a pneumatic cylinder (bottom portion).

FIG. 3 is a front view of the sitting device in FIG. 1. In FIGS. 1 and 3, one half seat has been removed for clarity.

FIG. 4 shows a more detailed height-adjusting mechanism.

FIG. 5 is a front view of the other side of the first embodiment of the sitting device. In FIGS. 5 and 6, one half seat has been removed for clarity.

FIG. 6 is a side view of the sitting device in FIG. 5.

FIG. 7 is an example of a sequence of positions by the first embodiment of the sitting device.

FIG. 8 shows a schematic circuit of the sitting device including a control box, a power supply and the actuators. The control box contains manual and automatic panels.

FIG. 9 shows two possible height positions with both of the half seats being in the supporting position.

FIG. 10 is a side view of the second embodiment of the sitting device. The lower part of the supporting arm has swung backward (as indicated by the curved arrow) and the half seat is retracted. The inset shows an equivalent retracting motion of a human arm.

FIG. 11 is a front view of the sitting device in FIG. 10.

FIG. 12 is a side view of the second embodiment of the sitting device. The lower part of the supporting arm has swung forward (as indicated by a curved arrow) and the half seat is in the supporting position. The inset illustrates a magnified view of the joint between the upper and lower parts of the supporting arm. For clarity, the joint has been separated.

FIG. 13. is a front view of the sitting device in FIG. 12. The inset illustrates a magnified view of the joint between the upper and lower parts of the supporting arm. For clarity, the joint has been separated.

FIG. 14. is a perspective views of the second embodiment of the sitting device with different heights and seat positions.

FIG. 15 is a perspective view of a third embodiment of the sitting device. Most of the configuration of this embodiment is similar to the one in the first embodiment but it adds two supporting columns for a better support of the sitting device.

FIG. 16 illustrates a configuration of the third embodiment having both of the half seats in supporting position with lowered height.

FIG. 17 is an alternative design of the half seat and its raising mechanism (upper panel). In this design many small segments of the half seat, instead of one monolithic half seat, rise or retract segment by segment in a sweeping motion. A corresponding swinging motion of the half seat in prior embodiments is illustrated the lower panel for a comparison purpose.

FIG. 18 shows a fourth embodiment where the two half seats are statically raised (i.e., at least no actuator-driven half seat raising/retracting mechanism is assumed) with a gap in between (left panel). The gap can be closed by bring the two halves closer together in a linear motion forming a full seat (right panel). Only the seat configuration is shown for clarity.

FIG. 19 shows a fifth embodiment where the two separated & statically raised half seats can be brought together by a pivoting motion. Only the seat configuration is shown for clarity.

FIG. 20 shows a sixth embodiment where the two half seats are individually controlled along the two fronto-caudal parallel rotating axes. Only the seat configuration is shown for clarity.

FIG. 21 shows a seventh embodiment where a statically raised full seat and a statically raised half seat (may be foldable manually) are positioned side by side with a gap in between. The user maneuvers to switch his/her positions between the two seats as he/she desires. Only the seat configuration is shown for clarity.

FIG. 22 shows an eighth embodiment where the actuator that raises the half seat is encased inside the crossbar of the seat frame, therefore exposing no damageable moving parts. Only the essential parts are shown for clarity.

FIG. 23 shows a ninth embodiment where a cable and pulley mechanism raises or retracts the half seats (only one side of the mechanism is shown for clarity). The pulley mechanism maybe housed in or around the armrest. Only the essential parts are shown for clarity.

FIG. 24 shows a tenth embodiment where a supporting beam and a half seat are shown. The moving support beam travels forward therefore push-raising the half seat, and positions itself to support the half seat. The supporting beam is supposed to be able to adjust its height to match the height of the seat. Only the essential parts are shown for clarity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a sitting device whose preferred embodiments are indicated by numbers, 1, 44, 45, 46, 65, 67, and also illustrated in FIGS. 17 to 24.

FIG. 1 shows a lateral view of a first embodiment of the sitting device where a user sits on one of the half seats, 2, while standing with his/her unsupported leg. For comfort, a foot stool, 9, is provided.

In a first embodiment and referring to FIGS. 1-9, the sitting device 1 includes a seat support frame or member, 3, 12 to which the rear end of a half seat 2 is secured; a linear actuator 4, is linked to a perch 5, 14 jutting out from the bottom part of the support frame 3, 12; the seat support frame 3, 12 is supported by a pneumatic cylinder 6, 17, or an equivalent mechanism, that could change the height of the sitting device via its piston 10 in FIG. 2 housed inside of the vertical guide tube part 11 of the support frame 3, 12. In this preferred embodiment, the pneumatic cylinder is a non-rotating one to prevent a pivoting motion of the sitting device around the cylinder.

FIG. 2 shows is an exploded, perspective view of a height adjustment mechanism of a sitting device according to the present invention. The seat supporting frame is comprised of a horizontal crossbar 13, a vertical guide tube 11 and two perches 14, 14 a with brackets 16, 16 a accepting the linear actuator 19. The crossbar 13 accepts the two half seats via the hinges 18, 18 a. A pneumatic cylinder 17 or other compatible height changing mechanism is inserted through the bottom of the guide tube. By lifting the height adjusting lever 15, 23 which pushes the gas releasing button, 40 in FIG. 4, on top of the piston 10, 40 of the gas cylinder 17, the piston 10 of the pneumatic cylinder changes the length, therefore changing the position of the seat supporting frame 12 relative to the pneumatic cylinder 17, in turn changing the height of the sitting device. At the bottom of the vertical guide tube, a band brake, 31, 38, or other height fixing mechanism is housed to fix the height. Fixing of the height is needed because the height of the sitting device needs to be stable to match the height of the user.

FIG. 3 shows a front view of the sitting device in FIG. 1. One half seat has been removed for clarity; the base part of the sitting device is illustrated as an environmental view to give a 3D sense; the same holds for the following figures. The position of the half seat 20 is controlled by a linear actuator 19 & 24. The bottom of the actuator is linked to the perch 21 via a bracket 16 and the top is linked to the bottom of the half seat via a bracket 22. When the piston of the actuator 24 lengthens it pushes the bottom of the half seat 20 therefore raises the half seat in a pivoting motion around the hinge 18 to a supporting position as shown in FIGS. 1 and 3. The illustration also includes a back support 8, 24, and a chair base 25 among other possible chair mechanisms.

FIG. 4 shows a more detailed height-adjusting mechanism. The figure illustrates a cross-section of the seat supporting frame comprised of a horizontal crossbar 26 a and a vertical guide tube 26 b; for clarity, the band-brake 31 and the pneumatic cylinder comprised of the piston 29 and its casing 30 are not sectioned. The crossbar 26 a houses a spring-loaded height-adjusting lever 27. The top part of the guide tube 26 b secures a socket 28 that secures the top of the piston 29 of the pneumatic cylinder 30 or any equivalent length-changing mechanism. The casing of a band brake 31 or equivalent height-fixing mechanism is secured at the bottom of the guide tube 26 b. The casing of the pneumatic cylinder 30 glides through the band brake 31 when the height is allowed to vary. The cable of the band brake 32 links the height-adjusting lever 27 and the band brake 31 and is protected by its case 33. The left panel of FIG. 4 shows the configuration of the height-adjusting mechanism when it is not in operation. During this non-height adjusting state, the spring 34 pulls the lever 27 down-ward and the cable of the band brake 32 is in a high tension pulled state, which in turn makes the band brake 31 chock the pneumatic cylinder casing 30 therefore fixing the height of the sitting device. The right panel in FIG. 4 shows the configuration of the height adjusting mechanism when it is in operation. When the height adjusting lever 35 is pushed up, as indicated by an up-ward arrow in the right panel of FIG. 4, the lever pivots around its pivot 36. This lifting motion makes the cable of the band brake 37 relax which in turn makes the band brake 38 release its grip on the pneumatic cylinder casing 39. After relaxing this height-fixing mechanism, the other end of the height adjusting lever pivots further down now pushing the gas-releasing button 40 on top of the piston of the pneumatic cylinder 41, which in turn varies the length of the pneumatic cylinder and therefore the height of the sitting device. When the height-adjusting lever 35 is released, the lever first releases the gas-releasing button 40 therefore stopping the motion of the pneumatic cylinder and then pulls the cable of the band brake 37 to fix the height. In summary, the lifting motion of the height-adjusting lever, by the user, 1) disables the height fix by releasing the grip of the band brake around the pneumatic cylinder and then; 2) engages height adjustment by pressing the gas-release button on top of the pneumatic cylinder. When the height-adjusting lever is released from the lifted position, it 1) disables the height changing mechanism by releasing the gas-releasing button on top of the pneumatic cylinder and then; 2) fixes the height by pulling the cable of the band brake.

FIGS. 5 and 6 show a front and lateral views of another side of the first embodiment of the sitting device. When the piston of the actuator 42 retracts, it leads the half seat 43 to a collapsed position, as illustrated in FIGS. 5 and 6, in a pivoting motion (indicated by a curved arrow) around the hinge 44. In FIGS. 5 and 6, one half seat has been removed for clarity.

FIG. 7 illustrates an example of a sequence of motions by the first embodiment of the sitting device. The user can use a control box 50 illustrated in FIG. 8 to control the positions and sequence of positions of the half seats as he/she desires. The control box provides a manual panel 51 and an automatic panel 52. When desired, the user can manually control the position of each half seat individually using the buttons (4 buttons: left seat up, left seat down, right seat up, right seat down) in the “Manual” panel 51, or program how frequently the seat positions need to change using the buttons in the Automatic panel 52. The automatic panel provides 5 buttons as illustrated in 52. The “Cycle on/off” button disables or enables the programmed cycle of seat position sequence. The other 4 buttons (54-57) each having an icon corresponding to a configuration of positions of the two half seats provide a means to set a sequence of seat positions. When one of these buttons is pressed, the number (representing minutes) or “N/A” (representing “disabled position”) indicated at the nearest part of the display panel 58 changes to another value (e.g., pressing the button 54 will increase the number 5 to 6). Each number indicates how long the configuration of the half seat positions should last. For example, the number 5 in the display panel 58 indicates that the configuration of “right half seat supporting and left half seat collapsed” should last 5 minutes before going to the next seat configuration. When one of these buttons is pressed the associated number on the display panel changes in a rotating manner: 0→1→2 . . . 60→N/A→0, covering an hour. According to this scenario, the display panel 58 in FIG. 8 shows a set of sequence of seat configurations (5, 3, 7, N/A) corresponding to the ones in FIG. 7; namely, 5 minutes of 45 (right side of the user gets supported; left leg standing), 3 minutes of 47 (the user freely stands with two legs) and 7 minutes of 49 (the left side of the user gets supported; right leg standing). If desired, the user can push the button 55 to include the normal sitting position (shown in the left panel of FIG. 9) in the sequence. The electrical circuit further includes the power supply 59 and the actuators 60. The figures of 46 and 48 in FIG. 7 illustrate transient positions of the moving half seats.

FIG. 9 left panel shows a configuration of the second embodiment of the sitting device, in which both of the half seats are in supporting position 61. When the height is lowered in combination with the raised half seats, the sitting device becomes an ordinary chair 62.

FIGS. 10 to 14 illustrate a second preferred embodiment of the sitting device. FIG. 10 and FIG. 11 show a side view and a front view of the second preferred embodiment of the sitting device 63, 69, 72, 79. For clarity, one half seat has been removed. Most of the mechanisms of the second embodiment of the sitting device are the same as the ones of the first embodiment except for the half seat moving mechanism. The second embodiment uses two swinging-motion seat supporting arms each one comprised of the lower part 64 and the upper part 65, in contrast to the linear actuator 19, 42 described in the first preferred embodiment. The lower part 64 and the upper part 65 of the seat supporting arm are linked by a shock absorber 67. The bottom of the lower part of the seat support arm 64 is attached to a slowly moving rotor 66, 70, which is in turn secured to a perch 71. When the rotor 66 in FIG. 10 spins clockwise the lower part of the half seat-supporting arm swings backward as illustrated by a curved arrow. This motion is equivalent to a movement of a human arm bending inward from a stretched position, as illustrated in the inset figure. This motion of the half-seat-supporting arm leads the attached half seat 68 to a retracted position.

FIGS. 12 and 13 show a side view and a front view of the second preferred embodiment of the sitting device 72, 79, respectively. When the lower part of the supporting arm 73 swings forward, indicated by a curved arrow, due to a rotating motion of the rotor 75, the supporting arm extends (or straightens) just like a stretching arm from a bent position therefore pushing the half chair 74, 80 to a supporting position. The inset shows the configuration of the joint portion 77 of the lower and upper parts of the support arm. For a better illustration it shows magnified and disjointed parts. The configuration of the joint prevents the angle of the arm from going beyond 180 degrees, just like a human arm that cannot be bent outward, i.e., locks (for axial force) when straight. The inset of the FIG. 13 shows the configuration of the joint 81 from another view point. This configuration allows the supporting arm to lock naturally when it is stretched just like a human arm.

The locked supporting arm as illustrated in FIG. 12 becomes unlocked during retraction of the half seat because the supporting arm bends. Without a motion damping mechanism, this will make the half seat collapse too quickly under the user's weight. To prevent this sudden yielding of the position of the half seat, a shock absorber 78 is attached linking the lower part 73 and upper part 76 of the supporting arm. While the supporting arm of this embodiment uses only two segments (lower part and upper part), many more segments can also be used. This may give a better retracting motion and also reduce the length that juts out backside of the chair when the half seat is in a retracted position.

The left panel of FIG. 14 is a perspective view of the second embodiment with one half seat raised and the other retracted 82. The right panel of FIG. 14 is a perspective view of the second embodiment having a configuration similar to the one in FIG. 9 right pane 62. When both of the half seats are in the supporting position they form a full seat and the sitting device can be used as an ordinary chair 83.

FIGS. 15 and 16 show a third preferred embodiment of the invention with heavy duty design using two supporting columns. FIG. 15 shows a perspective view of a third preferred embodiment of the invention 84. This embodiment 84 is an adaptation of the first embodiment 1, 61, 62 (could be of the second one, 82, 83) with two flanking supporting columns 85, 86 and two guide tubes 87, 88 that glide along the corresponding supporting columns. Armrests 89, 90 are secured at the top portion of the guide tubes 87 and 88. The middle column of the sitting device, which houses the height adjustment mechanism, is connected to the two guide tubes 87, 88 by two horizontal crossbars, 91, 92. The upper crossbar 91 secures the two half seats 97, 98; the lower crossbar 92 secures the bottom of the two actuators 94, 95 controlling the half seats. This reinforced design prevents the sitting device from a pitching motion when the half seats 97 and/or 98 are in supporting position and receive a heavy load.

The height adjustment mechanism of the third embodiment of the sitting device is similar to the ones in the first and second embodiments of the sitting device where the piston (similar to the one, 10, in FIG. 2) of the pneumatic cylinder 96 extends or retracts causing the height of the device to vary. As the height of the sitting device goes up or down the guide tubes 87 and 88 will glide up or down along the corresponding supporting columns 85 and 86, respectively. One example of a different sitting height is illustrated in FIG. 16 where the piston of the pneumatic cylinder has fully retracted therefore lowering the sitting position of the device 99, transforming the device into an ordinary chair.

The half seat raising/folding mechanism can be achieved using other alternative mechanisms. One non-limiting example is given in the upper portion of FIG. 17. This example shows an unfolding motion of a half seat, 100, comprising 3 small segments, rising (to the right in the figure) or retracting (to the left in the figure) segment by segment in a sweeping motion. For a comparison purpose, a corresponding swinging motion of one monolithic half seat, 101, used in the first and second preferred embodiments of the sitting device, is shown in the lower portion of FIG. 17. This gradual unfolding of the seat illustrated in the upper portion of FIG. 17 may achieve a less intrusive motion for the user than the one illustrated in the lower portion of FIG. 17. Only the moving components of the half seat are shown for clarity.

FIG. 18 shows a fourth embodiment of the sitting device; only the half seat configurations are shown for clarity. This embodiment includes two half seats, 102-105, statically raised (i.e., no actuator-driven half seat raising/lowering mechanism is assumed) with a gap in between. The user manually changes his position to sit on the right half seat or left half seat while maintaining a standing posture with the unsupported leg; one example is illustrated in the left panel of FIG. 18. The gap can be closed by bring the two halves 104, 105 closer together in a linear motion (as illustrated by the two opposing arrows in the right panel in FIG. 18) forming a full seat. This linear motion can be achieved manually or automatically.

FIG. 19 shows a fifth embodiment of the sitting device; only the half seat configurations are shown for clarity. This embodiment includes two half seats 106˜109 statically raised. The user manually changes his position to sit on the right half seat or left half seat while maintaining a standing posture with the unsupported leg. The two separated and statically raised half seats 106, 107 can be brought together by a pivoting motion as illustrated by two curved and opposing arrows along a pivoting axis (illustrated by a vertical broken line on the right panel of FIG. 19) to form a full seat 108, 109. This pivoting motion can be achieved manually or automatically.

FIG. 20 shows a sixth embodiment of the sitting device; only the half seat configurations are shown for clarity. The embodiment includes two half seats 110˜113 whose positions are individually controlled along the two fronto-caudal rotating axes on the left and right side of the user who is in the middle of them. This rotating motion, illustrated as arrows, can be achieved manually or automatically.

FIG. 21 shows a seventh embodiment of the sitting device; only the seat configurations are shown for clarity. The embodiment includes a statically raised full seat 114 and a statically raised half seat 115 (may be foldable or removable manually) with a gap in between. The user maneuvers to switch his/her positions between the two seats as desired.

FIG. 22 shows an eighth embodiment of the sitting device; only the essential parts are shown for clarity. In FIG. 22, the left panel illustrates a side view of a raised half seat 117; the middle panel illustrates a perspective view of the raised and folded half seats 118 and 122; the right panel illustrates a side view of a retracted half seat 123. In this design, the actuators that raise the half seats are encased inside the crossbar 120 of the seat support frame (assuming a similar height adjusting mechanism as the one used in the first and second embodiment of the sitting device) therefore exposing no damageable moving parts of the actuating mechanism. One side rotor 116, 119 of an actuator is connected to the corresponding half seat 117, 118 and the other side rotor 121, 124 of another actuator is connected to the other half seat 122, 123. When a rotor 116 rotates anticlockwise, illustrated as upward-curved arrows in the left and middle panels of FIG. 22, the attached half seat 117, 118 rises to a supporting position. When the rotor 121, 124 rotates anticlockwise, illustrated as downward-curved arrows in the middle and right panels of FIG. 22, the attached half seat 122, 123 retracts.

FIG. 23 shows a ninth embodiment of the sitting device. The left panel of FIG. 23 shows a perspective view of a half seat in a retracted position, and the right panel shows a perspective view of the same half seat in a raised position. Only one side of the half-seat-position-adjusting mechanism is shown for clarity. This embodiment includes a cable 127,131; a pulley 126, 132; a motor 128, 133 that pulls or releases the cable; and a half seat 129, 134 whose backend is attached preferably to the seat support frame (not shown and assumed a similar configuration as the one used in the first and second embodiment of the sitting device) via a hinge 125, 135. When one end of the cable 131 is pulled down, illustrated as a downward arrow on the right panel, the other side of the cable, whose end is attached to the half seat 129, 134 via a link 130, 136 gets pulled upward, illustrated as an upward arrow. This upward motion of the cable raises the half seat, illustrated as an upward curved arrow. The pulley mechanism may be housed in or around the armrest.

FIG. 24 shows a tenth embodiment of the sitting device; only one side of the half seat raising mechanism is shown for clarity. This embodiment includes a supporting beam 139, a half seat 137 and the seat support frame 138. When the moving supporting beam 139 travels forward (from the left-most figure to the right-most figure) it pushes the retracted half seat to a raised position (right-most panel). A backward travel motion will let the half seat go back to the retracted position (left-most panel). The supporting beam is supposed to be able to adjust its height to match the seat height that the user sets.

REFERENCES CITED Academic Journals

-   1. Deyo R A, Mirza S K, Martin B I. (2006) Back pain prevalence and     visit rates: estimates from U.S. national surveys, 2002. Spine     (Phila Pa. 1976). 31:2724-2727 -   2. Kelsey J L, White A A. (1980) Epidemiology and impact of low back     pain. Spine, 5:133-142. -   3. Lis A M, Black K M, Korn H, Nordin M. (2007) Association between     sitting and occupational LBP. Eur Spine J. 16:283-298. -   4. Bathe M C, Videman T, Gibbons L E, Manninen H, Gill K, Pope M,     Kaprio J. (2002) Occupational driving and lumbar disc degeneration:     a case control study. Lancet. 360:1369-1374. -   5. Mendelek F, Kheir R B, Caby I, Thevenon A, Pelayo P. (2011) On     the quantitative relationships between individual/occupational risk     factors and low back pain prevalence using nonparametric approaches.     Joint Bone Spine. PMID: 21549633. -   6. De Carvalho D E, Soave D, Ross K, Callaghan J P. (2010) Lumbar     spine and pelvic posture between standing and sitting: a radiologic     investigation including reliability and repeatability of the lumbar     lordosis measure. J Manipulative Physiol Ther. 33(1):48-55. -   7. O'Sullivan P B, Smith A J, Beales D J, Straker L M. (2011)     Association of biopsychosocial factors with degree of slump in     sitting posture and self-report of back pain in adolescents: a     cross-sectional study. Phys Ther. 91(4):470-83. -   8. Lengsfeld M, Frank A, van Deursen D L, Griss P. (2000) Lumbar     spine curvature during office chair sitting. Med Eng Phys.     22(9):665-9

United States Patents

4,765,684 August 1988 Kvalheim et al. 5,782,534 July 1998 Desanta 3,704,847 December 1972 Schmitt 4,738,487 April 1988 Shalinsky et al. 4,451,086 May 1984 Seven 7,387,339 B2 June 2008 Bykov et al. 6,139,095 October 2000 Robertshaw 6,357,827 B1 March 2002 Brightbill et al. 

1. A sitting device enabling a user to sit with one side of a lower portion of the body of the user supported, while enabling the user to maintain a standing posture with an unsupported leg of the user.
 2. The sitting device according to claim 1, comprising two half seats split along a midline whereby one half seat supports the one side of the lower portion of the body of the user.
 3. The sitting device according to claim 2, further comprising a foot stool for the foot to rest on in case the foot is raised.
 4. The sitting device according to claim 2, wherein the half seats can be individually raised to a horizontal position or lowered to a vertical position thereby enabling the user to use the device as an ordinary chair by having both of the two half seats in horizontal position and enabling the user to freely stand by lowering both half seats to the vertical position.
 5. The sitting device according to claim 4, a mechanism for raising and lowering the half seats of the sitting device including a controller having raise/lower buttons to change the positions of the half seats individually.
 6. The sitting device according to claim 5 wherein the controller includes a programmable timer to define how frequently the half seats change positions (or alternate) through a sequence of postures of the user's choice.
 7. The sitting device according to claim 2, further comprising a seat support frame, two half-seat-position-adjusting actuators, the frame including a horizontal crossbar and a vertical guide tube, wherein a backend of each of the two half seats are pivotally secured on the horizontal bar, the vertical guide tube housing a length-changing mechanism to vary the height of the sitting device and a height fixing mechanism which prevents yielding of the height of the sitting device when the user sits, the two half-seat-position-adjusting actuators being attached at one end of each to the vertical tube and at the other end to the respective half seat.
 8. The sitting device according to claim 7, wherein the height fixing mechanism includes a band brake, the length-changing mechanism includes a pneumatic cylinder, and the sitting device further comprises a height-adjusting lever operatively connected with the length-changing mechanism and the height fixing mechanism such that by lifting motion of the height-adjusting lever, the user 1) disables the height fix by releasing the grip of the band brake around the pneumatic cylinder and then; 2) engages height adjustment by pressing the gas-release button on top of the pneumatic cylinder, and when the height-adjusting lever is released from the lifted position, the user 1) disables the height changing mechanism by releasing the gas-releasing button on top of the pneumatic cylinder from its pressed state and then; 2) fixes the height by pulling the cable of the band brake.
 9. The sitting device according to claim 7 wherein the two half-seat-position-adjusting actuators comprise linear motion actuators to raise or lower the half seats, a bottom part of each actuator being secured to the lower portion of the vertical guide tube, a top part of the actuator being secured to the bottom of the respective half seat via a bracket.
 10. The sitting device according to claim 7 wherein the two half-seat-position-adjusting actuators comprise a rotor and a supporting arm for each half seat having a bottom is attached to the rotor and a top part attached to the bottom of the half seat, the supporting arm locks when a lower part of the arm and an upper part of the arm form a substantially straight line thereby preventing yielding of the seat position even when the user sits.
 11. The sitting device according to claim 10 wherein each half-seat-position-adjusting actuator further includes a shock absorber to prevent a sudden sinking motion of the half seat when the supporting arm retracts from the locked supporting position.
 12. The sitting device according to claim 4 wherein each a half seat comprises many small segments linked pivotally together.
 13. The sitting device according to claim 2, wherein the two half seats are statically positioned with a gap in between, the gap being closeable by bring the two half seats closer together in a linear lateral motion forming a full seat.
 14. The sitting device according to claim 13 wherein the two separated statically positioned half seats can be brought together by a pivoting motion.
 15. The sitting device according to claim 2, wherein the positions of two half seats are individually controlled along two fronto-caudal rotating axes.
 16. The sitting device according to claim 1, including a statically raised full seat and a statically raised half seat with a gap in between, whereby the user maneuvers to switch positions between the two seats as desired.
 17. The sitting device according to claim 2, further comprising a seat support frame, two half-seat-position-adjusting actuators, the frame including a horizontal crossbar and a vertical guide tube, wherein a backend of each of the two half seats are pivotally secured on the horizontal bar, the actuators being encased inside the crossbar and including a rotor attached to the crossbar, therefore exposing no damageable moving parts of the actuating mechanism.
 18. The sitting device according to claim 7, wherein the actuators each include a cable and pulley mechanism to raise or retract the half seats.
 19. The sitting device according to claim 2, wherein the actuators include two individually controlled supporting beams, one for each half seat, the beams being static for a given height of the sitting device, each supporting beam traveling along the fronto-caudal axes of the sitting device, whereby when the respective beam travels forward the beam push-raises the corresponding half seat using its statically raised height and positions itself to support the bottom of the half seat.
 20. The sitting device according to claim 2, further comprising armrests, a back support and one of casters and a base including a turn table, to allow movement or rotation of the whole sitting device. 